The Corridor Mate is a checkmate pattern that features the enemy king that can’t escape from check because it’s trapped along a rank, file or diagonal (corridor). This type of checkmate is sometimes referred to as the Back Rank Mate but it’s not quite the same thing. (The Corridor Mate is actually a broad term for a number of checkmate ideas, one of which is the Back Rank Mate).
Corridor Mate Example 1
The first example illustrates the checkmate pattern on a rank.
Diagram above: Rd8# is known as a Back Rank Checkmate. In this case the 8th rank represents the “corridor”.
Corridor Mate Example 2
The second example illustrates a checkmate pattern executed on a file:
Diagram above: 1.Qc2+ proves the black king is trapped in a corridor on the c-file. The best black can do is to delay the checkmate with 1… Qc3 (or Qc5), in which case white will simple capture the black queen, 2.Qxc5, and say checkmate.
Corridor Mate Example 3
The last example illustrates a corridor mate on a diagonal:
Diagram above: 1.Rb8+ Qg8 2.Be5# demonstrates the corridor checkmate along a diagonal.
Diagram above: 2.Be5# demonstrates how the black king is trapped on the e5-h8 diagonal. Note that the black queen is pinned by the rook.